This invention relates generally to the field of macroscopically manipulable nanoscale devices that permit information to be provided to or obtained form a nanoscale environment, and more particularly to the use of nanotubes attached to macroscale mounting members as nanoscale probes, fabricators and manipulators.
The development of mechanical, electrical, chemical and biological devices and systems that include or comprise nanoscale components, sometimes termed nanotechnology, has been slowed by the unavailability of or limitations inherent in devices that enable sensing, measuring, analyzing, and modifying objects with nanometer resolution and sensing, measuring, analyzing, moving, manipulating, fabricating and modifying objects with nanometer dimensions.
One class of devices that have found some use in nanotechnology applications are proximity probes of various types including those used in scanning tunneling microscopes (STM, atomic force microscopes (AFM and magnetic force microscopes (MFM). While good progress has been made in controlling the position of the macroscopic probe to sub-angstrom accuracy and in designing sensitive detection schemes, the tip designs to date have a number of problems.
One such problem arises from changes in the properties of the tip as atoms move about on the tip, or as the tip acquires an atom or molecule from the object being imaged Another difficulty with existing probe microscope tips is that they typically are pyramidal in shape, and that they are not able to penetrate into small xe2x80x9cholesxe2x80x9d on the object being imaged, and they may give false image information around sharp vertical discontinuities (e.g., steps) in the object being imaged, because the active portion of the xe2x80x9ctipxe2x80x9d may shift from the bottom atom to an atom on the tip""s side. Moreover, conducting conventional probe microscope tips have never been successfully covered with an insulating material so that the only electrically-active element is the point of the tip itself.
Conventional probe microscope tips also are very rigid in comparison to many of the objects to be examined, and with xe2x80x9csoftxe2x80x9d samples (e.g., biomolecules like DNA) conventional AFM tips misrepresent the thickness of the object imaged, because that object is literally compressed by the action of the tip.
Thus, there is a need for macroscopically manipulable nanoscale devices for observing, fabricating or otherwise manipulating individual objects in a nanoscale environment that address the foregoing and other disadvantages of the prior art.
The present invention employs geometrically-regular molecular nanotubes (such as those made of carbon) to fabricate devices that enable interaction between macroscopic systems and individual objects having nanometer dimensions. These devices may comprise one or more individual nanotubes, and/or an assembly of nanotubes affixed to a suitable macroscopically manipulable mounting element whereby the device permits macroscale information to be provided to or obtained from a nanoscale environment.
Individual nanotubes or bundles of nanotubes can be recovered from a material (such as the carbon nanotube xe2x80x9cropesxe2x80x9d) grown by procedures described herein. Assemblies of nanotubes can be fabricated by physical manipulation of nanotube-containing material, or by self-assembly of groups of nanotubes, or by chemical, physical, or biological behavior of moieties attached to the ends or to the sides of the nanotubes or bundles of nanotubes. Individual nanotubes or assemblies of nanotubes can be grown to achieve specific characteristics by methods described herein.
More particularly, the devices of the present invention can comprise probes with tips comprising one or more molecular nanotubes. When attached to an appropriate motion transducer (piezoelectric, etc.) the probe is capable of sensing, measuring, analyzing, and modifying objects with nanometer resolution and sensing, measuring, analyzing, moving, manipulating, and modifying objects with nanometer dimensions.
A method for making such devices is disclosed, which includes the steps of (1) providing a nanotube-containing material; (2) preparing a nanotube assembly comprising at least one nanotube from the nanotube-containing material; and, (3) attaching the nanotube assembly to a macroscopically manipulably mounting element.
The nanoscale devices according to the present invention provide strong, reliably mounted probe tips and other nanoscale fabricators and manipulators, that are gentle, hard to damage, even upon xe2x80x9ccrashingxe2x80x9d into the working surface, that can be easily made electrically conductive, that can present a uniform diameter and precisely known atomic configuration, including precisely located derivitization with chemical moieties.
The devices of the present invention have a number of advantages over conventional microscopy probes (e.g. STM and AFM). A probe tip consisting of a single molecular nanotube or a few such tubes has the advantage that all its constituent atoms are covalently bonded in place and are unlikely to move, even under extreme stress, such as that occurring when the tip xe2x80x9ccrashesxe2x80x9d into the object being imaged. Moreover, the known, stable geometry of molecular nanotube tips allows one to more accurately interpret the data acquired by probe microscopes using such tips. In addition, molecular nanotubes are very compliant, buckling in a gentle, predictable, and controllable fashion under forces that are small enough to avoid substantial deformation to delicate sample objects. Unlike currently used pyramidal probe tips, molecular nanotubes are very long with respect to their diameter, and can therefore reliably image the bottom areas of holes and trenches in the items being imaged.
Electrically conducting nanotube tips can be coated with an insulating material to achieve localized electrical activity at the end of the probe element. This geometry facilitates probing of electrochemical and biological environments.
Molecular nanoprobe elements have remarkably different chemical activity at their ends because the atomic configuration on the ends differs fundamentally from that of the sides. Consequently, one can selectively bond specific molecules to the tip end. This site specific bonding enables chemically-sensitive probe microscopy, and a form of surface modification in which some superficial atoms or molecules of the object being imaged react chemically with the probe tip or species attached or bonded to it. This delicate chemistry enables a form of surface modification that is not possible with conventional tips. This surface modification can serve as a direct manipulation technique for nanometer-scale fabrication, or as a method of lithography in which a xe2x80x9cresistxe2x80x9d is exposed by the chemical or electrochemical action of the tip.